1. Field of the Invention
The present invention relates to a method and apparatus usable with a calibration device for measuring the radioactivity of a sample. More particularly, the invention provides a method for reducing unnecessary radiation exposure during the measurement of the radioactivity of a sample in a calibration device. Further, the invention provides an apparatus or device for handling a container of the radioactive material or solution so as to minimize unnecessary radiation exposure.
2. Description of the Prior Art
Reduction of unnecessary radiation exposure is a long recognized need. For instance, measurement of a very strong radionuclide source is often required in hospitals and radiopharmacies for diagnostics and/or therapy of patients. It is important to minimize exposure during such measurement.
Tc-99m (technetium-99m) is the most commonly used radionuclide in a hospital. Tc-99m is often obtained by eluting Mo-99 (molybdenum-99, a Tc generator). Eluate must be measured for its activity and for contamination by Mo-99 in order to ensure safety of the patient.
Dose calibrators (such as a radioisotope calibrator of the type manufactured by Capintec, Inc., of Ramsey, N.J.) are most commonly used to measure activity of radionuclide samples in a hospital. Mo-99 contamination in an eluted Tc-99m sample is often measured by a dose calibrator by placing the sample in a filter, such as a "Mo Assay Cannister".
These processes often necessitate handling of strong radionuclides, hence, exposure to strong radiation field. Activity of a strong Tc-99m source and Mo-99 contamination in the sample can be measured while the sample is shielded, when used in conjunction with a shielded dose calibrator, such as Capintec's models CRC-50, 30, and 10 calibrators.
A known handling apparatus uses a cannister having a cannister body engaged with a cannister base. The bottom of the cannister base is designed to cooperate with the floor of the calibration device so that the base remains stationary during rotation of the cannister body. After the body has been separated from the base, the body is removed from the calibration device so that a measurement can be performed. When the measurement is completed, the body is reinserted into the calibration device and rotated so as to engage the base.
Problems encountered with this system include realignment problems between the cannister body and base when the body is reinserted into the calibration device, and the necessity to apply both an axial force and a torque to the cannister body during engagement and disengagement of the cannister body from the base.